Conventionally, there have been proposed various methods in which a specific component in a living body or in a solution are measured by using an optical measuring device. For example, there has been known a method in which a blood-sugar level is measured by bringing upper and lower lips into intimate contact with a transparent attenuated total reflectance (ATR) element having a pair of reflecting surfaces facing in parallel.
In this method, an ATR element which is an ATR prism comprising zinc selenide, silicon, or germanium is held in a mouth, and a light is applied to the ATR element while the ATR element is pressed by the lips, and an analysis is conducted for a light emitted to the outside of the ATR element after total reflections are repeated between the reflecting surfaces of the ATR element and the lips.
In the above method, evanescent wave (so-called penetrating light) is applied to a quantitative analysis. A light traveling in the ATR prism is reflected, after slightly going into lips. Therefore, the light is affected by each component in a body fluid existing in the lips.
For this reason, variations in reflectance and absorptance of a body fluid can be detected by measuring the amount of the reflected light, thereby enabling to obtain information about each component in the body fluid.
In Japanese Laid-Open Patent Publication No. Hei 11-178799, for example, there has been disclosed a method in which properties and characteristics of surface layer tissues, preferably skin tissues or mucous membrane tissues, further preferably dermis tissues or subcutaneous tissues in the skin tissues, or lamina propria mucosae or submucosal layer in mucous membrane tissues of a living body are analyzed by light absorption.
In this method, a part of surface layer tissues of a living body is protruded by using a groove, and a spectrum analysis is conducted by light receiving and applying operations from a light emission part and to a light incident part facing each other interposing the protruded part in between.
Based on this method, sufficient signals for the measurement can be obtained, and information of the living body components can be obtained even with a usage of near-infrared light of 1.4 to 2.5 micrometers, which is absorbed by living body in a greater degree. Additionally, an optical path length of the light transmitting the living body can be determined from the size of the groove. It is known from the Lambert-Beer Law that a light absorption amount of a living body is proportional to the optical path length.
Thus, the fact that the optical path length can be automatically determined from the size of the groove has quite significant meaning in measurements using light, and is a great advantage in this method.
Also, International Publication No. WO 01-58555 recites a contact element (optical measurement device) for measuring information of living body comprising an abutting means having a recess for abutting the living body, a detecting light emission means which emits the detecting light from a part in the recess, and a detecting light incident means provided in other part in the recess for applying the detecting light, characterized in that the detecting light is applied to the detecting light incident means after passing through the living body tissue inserted in the recess, while the abutting means abutting the living body tissues. The contact element is proposed by an intention to improve the contact between a surface of the living body and an optical censor for improving measurement accuracy.